JP5690915B2 - Non-wetting coating on fluid ejection device - Google Patents

Description

  The present specification relates to a coating on a fluid ejection device.

  A fluid ejection device (eg, an ink jet print head) typically has an inner surface, an orifice through which fluid is ejected, and an outer surface. As fluid is ejected from the orifice, fluid may accumulate on the outer surface of the fluid ejection device. As fluid accumulates on the outer surface near the orifice, further fluid expelled from the orifice can be diverted or completely blocked from the intended path of travel by interaction with the accumulated fluid (eg, by surface tension). there's a possibility that.

  Non-wetting coatings such as Teflon® and fluorocarbon polymers can be used to coat the surface. However, Teflon and fluorocarbon polymers are usually soft and not durable coatings. These coatings are also expensive and difficult to pattern.

  In one aspect, a fluid ejection device includes a substrate having an outer surface and an inner surface defining a fluid flow path to an orifice in the outer surface, covering at least a portion of the outer surface and substantially present in the flow path. Non-wetting coating. The non-wetting film is composed of molecular aggregates.

Embodiments may include one or more of the following. An inorganic seed layer having a composition different from that of the substrate may cover the inner surface and the outer surface of the substrate, and the non-wetting film may be disposed directly on the seed layer. The substrate may be composed of single crystal silicon, and the seed layer may be silicon oxide. The non-wetting film may be placed directly on the substrate. Non-wetting coatings include molecules with carbon chains terminated at one end with a CF ₃ group. The non-wetting coating is composed of at least one precursor of the group consisting of tridecafluoro 1,1,2,2 tetrahydrooctyltrichlorosilane (FOTS) and 1H, 1H, 2H, 2H perfluorodecyl-trichlorosilane (FDTS). It may contain molecules that are The non-wetting coating may have a thickness of 50 to 1000 angstroms. The non-wetting coating may comprise a plurality of identical molecules that are retained within the molecular assembly by substantially intermolecular forces with substantially no chemical bonds.

  In another aspect, a method of forming a non-wetting film on a fluid ejection device includes: maintaining the fluid ejection device in a chamber at a first temperature; and a precursor of the non-wetting film at a first temperature. Flowing into the chamber at a higher second temperature.

  Embodiments may include one or more of the following. The support in the chamber holding the fluid ejection device may be maintained at a lower temperature than the gas manifold for supplying precursor gas to the chamber. The temperature difference between the support and the gas manifold may be at least 70 ° C. The support may be cooled to a temperature below room temperature, and the gas manifold may be maintained above room temperature. The support may be maintained at room temperature and the gas manifold may be heated to a temperature above room temperature. The precursor may include at least one of tridecafluoro 1,1,2,2 tetrahydrooctyltrichlorosilane (FOTS) or 1H, 1H, 2H, 2H perfluorodecyl-trichlorosilane (FDTS). The non-wetting film may be removed from the inner surface that defines the fluid ejection flow path of the fluid ejection device.

  In another aspect, a fluid ejection device includes a substrate having an outer surface and an inner surface defining a fluid flow path to an orifice in the outer surface, and a seed layer covering at least the outer surface of the substrate and having a composition different from the substrate. A non-wetting coating on the seed layer that covers at least a portion of the outer surface and is substantially non-existent in the flow path. The seed layer includes water molecules trapped in the inorganic matrix. The seed layer includes an inner portion and an outer portion that is farther from the substrate than the inner portion. The outer part has a higher concentration of water molecules than the inner part.

  Embodiments may include one or more of the following. The seed layer may have a total thickness up to about 200 nm. The outer portion may have a thickness of about 50-500 angstroms. The base material of the seed layer may be an inorganic oxide. The inorganic oxide may be silicon dioxide. The non-wetting coating may include a siloxane bonded to silicon dioxide. The seed layer may cover the inner surface.

  In another aspect, a method of forming a non-wetting film on a fluid ejection device includes depositing a seed layer containing water molecules trapped in an inorganic matrix on an outer surface of a substrate; Depositing on the seed layer. The layer deposition step includes depositing the inner portion of the seed layer on the substrate at a ratio of the partial pressure of the first water and the partial pressure of the base material precursor, and the second water larger than the first ratio. Depositing the outer portion of the seed layer on the inner portion at a ratio of the partial pressure to the partial pressure of the matrix precursor.

Embodiments may include one or more of the following. The inorganic base material may be silicon dioxide. The substrate may be single crystal silicon. The non-wetting coating may include siloxane chemically bonded to the seed layer. The base material precursor may contain SiCl ₄ . The first H ₂ O: SiCl ₄ ratio may be less than 2: 1. The second H ₂ O: SiCl ₄ ratio may be greater than 2: 1. The outer portion may have a thickness of about 50-500 angstroms.

  In another aspect, a fluid ejection device includes a substrate having an outer surface and an inner surface defining a fluid flow path to an orifice in the outer surface, and covering at least a portion of the outer surface of the substrate and having a composition different from that of the substrate. A seed layer and a non-wettable coating on the seed layer that covers at least a portion of the outer surface and is substantially absent in the flow path. The seed layer includes an inner portion having a first density and an outer portion that is further from the substrate than the inner portion, the outer portion having a second density that is higher than the first density.

Embodiments may include one or more of the following. The seed layer may include silicon dioxide. The substrate may be single crystal silicon. The non-wetting coating may include siloxane chemically bonded to the seed layer. The first density may be about 2.0 g / cm ³ . The second density may be at least 2.4 g / cm ³ (eg, about 2.7 g / cm ³ ). The second density may be at least about 0.3 g / cm ³ higher than the first density. The outer portion may have a thickness of about 40 angstroms.

  In another aspect, a method of forming a non-wetting film on a fluid ejection device includes depositing a seed layer on an outer surface of a substrate, applying oxygen plasma to the seed layer on the outer surface, and a non-wetting film. Depositing on the seed layer on the outer surface.

Embodiments may include one or more of the following. A seed layer may be deposited on the inner surface of the substrate that defines a fluid flow path to an orifice in the outer surface. A non-wetting coating may be deposited on the inner surface. The non-wetting film on the inner surface may be removed. The seed layer may include silicon dioxide. The substrate may be single crystal silicon. The non-wetting coating may include siloxane that is chemically bonded to the seed layer. At least a portion of the seed layer may be deposited at a ratio of the partial pressure of water and the partial pressure of the matrix precursor that is greater than the ratio of the matrix that is consumed in the chemical reaction that forms the silicon oxide. The base material precursor may contain SiCl ₄ . The ratio of the partial pressure of water and the partial pressure of the matrix precursor may be greater than 2: 1.

  Some embodiments may have one or more of the following advantages. The outer surface surrounding the orifice can be non-wetting and the inner surface in contact with the fluid to be ejected can be wettable. Non-wetting coatings can reduce fluid accumulation on the outer surface of the fluid ejection device, thereby improving the reliability of the fluid ejection device. Non-wetting coatings can be denser, which makes them non-wetting and more durable and insoluble to a wider range of fluids. The seed layer under the non-wetting coating can be denser, thereby making the seed layer more durable and insoluble for a wider range of fluids. The non-wetting film can be thicker, which can improve the durability of the non-wetting film. The overcoat layer can cover the inner surface of the fluid ejection device. A highly wettable overcoat layer on the surface in contact with the fluid being ejected can improve control over droplet size, ejection speed, and other fluid ejection characteristics.

FIG. 1A is a cross-sectional view of an exemplary fluid ejection device. 1B is an enlarged view of a nozzle of the fluid ejection device in FIG. 1A. FIG. 2A is a schematic diagram of a non-wetting film monolayer. FIG. 2B is a schematic view of a non-wetting film assembly. FIG. 2C is a schematic diagram of an exemplary molecular chemical structure of a non-wetting coating. FIG. 3A illustrates an exemplary process for forming a fluid ejection device. FIG. 3B illustrates an exemplary process for forming a fluid ejection device. FIG. 3C illustrates an exemplary process for forming a fluid ejection device. FIG. 3D illustrates an exemplary process for forming a fluid ejection device. FIG. 3E illustrates an exemplary process for forming a fluid ejection device. FIG. 3F illustrates an exemplary process for forming a fluid ejection device. FIG. 3G illustrates an exemplary process for forming a fluid ejection device. FIG. 4 is a cross-sectional view of a nozzle in another exemplary fluid ejection device that does not include a seed layer of non-wetting coating. FIG. 5A is a cross-sectional view of a nozzle in another exemplary fluid ejection device that includes an overcoat layer. FIG. 5B shows one stage in an exemplary process for forming the fluid ejection device shown in FIG. 5A.

  FIG. 1A is a cross-sectional view of a fluid ejection device 100 (e.g., a nozzle of an inkjet printhead), and aspects not discussed herein are described in U.S. Patent Application Publication No. 2008-0020573 (hereby incorporated by reference in its entirety). (Incorporated in the text).

  The fluid ejection device 100 includes a substrate 102 on which a fluid channel 104 is formed. The substrate 102 can include a flow path body 110, a nozzle layer 112, and a film layer 114. The fluid flow path 104 can include a fluid inlet 120, an ascending path 122, a pump chamber 124 adjacent to the membrane layer 114, a descending path 126, and a nozzle 128 formed through the nozzle layer 112. . Each of the flow path body 110, the nozzle layer 112, and the film layer 114 may be silicon (for example, single crystal silicon). In some embodiments, the channel body 110, the nozzle layer 112, and the membrane layer 114 are fused together (inter-silicon bond). In some embodiments, the channel module 110 and the nozzle layer 112 are part of a monolithic body.

  An actuator 130 is placed on the membrane layer 114 above the pump chamber 124. The actuator 130 can include a piezoelectric layer 132, a lower electrode 134 (eg, a ground electrode), and an upper electrode 136 (eg, a drive electrode). In operation, the actuator 130 deflects the membrane layer 114 above the pump chamber 124, pressurizing liquid (eg, ink (eg, aqueous ink)) in the pump chamber 124, and the liquid flows through the descending path 126 to the nozzle. It is discharged through a nozzle 128 in the layer 112.

An inorganic seed layer 140 covers the outer surface of the nozzle layer 112 and the inner surface of the substrate 102 that defines the flow path 110. The inorganic layer 140 may be made of a material that promotes adhesion of a silane or siloxane film, such as an inorganic oxide (eg, silicon dioxide (SiO ₂ )). The thickness of the oxide layer may be about 5 nm to about 200 nm. Optionally, as shown in FIG. 1B, the outer portion 142 of the inorganic layer 140 can have a higher density than the rest of the inorganic layer 140. For example, the outer portion 142 can have a density of 2.4 g / cm ³ or greater (eg, 2.7 g / cm ³ ), and the inner portion can have a density of about 2.0 g / cm ³ . The outer portion 142 can have a thickness of about 60 angstroms or less (eg, about 40 angstroms thick). Increasing the density of the outer portion of the seed can increase durability and insolubility for a wider range of fluids. Alternatively, the inorganic layer 140 may consistently have approximately the same density.

  Optionally, as shown in FIG. 1B, the outer portion 144 of the inorganic layer 140 can trap water at a higher concentration than the rest of the inorganic layer 140. The thickness of the outer portion 144 is about 50-500 angstroms. By increasing the water concentration, the concentration of —OH groups on the surface of the inorganic layer 140 can be increased, thereby increasing the concentration of the adhesion points of the molecules of the non-wetting film, thereby increasing the density of the non-wetting film. . However, higher concentrations of -OH groups at the surface of the inorganic layer 140 may also reduce the chemical resistance of the inorganic layer itself. Alternatively, the inorganic layer 144 may consistently have approximately the same water concentration.

  The outer portion 144 having a high water concentration and the outer portion 142 having a high density may be present individually or in combination.

  A non-wetting coating 150 (eg, a layer of hydrophobic material) covers the inorganic layer 140 on the outer surface of the fluid ejection device 100, for example, no non-wetting coating is present in the flow path 104. As shown in FIG. 2A, the non-wetting coating 150 may be a self-assembled monolayer, ie a layer of a single molecule. The thickness of such a non-wetting film monolayer 150 is about 10-20 angstroms (eg, about 15 angstroms). Alternatively, as shown in FIG. 2B, the non-wetting film 150 may be a molecular assembly. Within a molecular assembly, the molecules 152 are separated from each other but are held as an assembly by intermolecular forces (eg, hydrogen bonds and / or van der Waals forces) rather than ionic or covalent bonds. The thickness of such a non-wetting coating assembly 150 is about 50 to 1000 angstroms. Increasing the thickness of the non-wetting coating makes the non-wetting coating more durable and resistant to a wider range of fluids.

Non-wetting film molecules can include one or more carbon chains terminated at one end by a —CF ₃ group. The other end of the carbon chain may be terminated with a SiCl ₃ group, or when the molecule is bonded to the silicon oxide layer 140, it may be terminated with a Si atom bonded to an oxygen atom in the silicon oxide layer. (The remaining bonds of Si atoms may be filled with oxygen atoms, OH groups, or both, which are also bonded to terminal Si atoms of adjacent non-wetting film molecules. In general, non-wetting The higher the density of the functional coating, the lower the concentration of such OH groups). The carbon chain may be fully saturated or partially unsaturated. For some of the carbon atoms in the carbon chain, the hydrogen atom can be replaced with fluorine. The number of carbons in the carbon chain may be 3-10. For example, the carbon chain could be (CH ₂ ) _M (CF ₂ ) _N CF ₃ (where M ≧ 2, N ≧ 0, M + N ≧ 2, eg (CH ₂ ) ₂ (CF ₂ ) ₇ CF _3).

  As shown in FIG. 2C, the molecules of the non-wetting coating (ie, a monolayer or part of a molecular assembly adjacent to the substrate) adjacent to the substrate 102 form a bond with the silicon oxide of the inorganic layer 140. Siloxane may be used.

  The process of forming a non-wetting film on a fluid ejection device (eg, an inkjet printhead nozzle) begins with an uncoated substrate 102, as shown in FIG. 3A. The uncoated substrate 102 may be composed of single crystal silicon. In some embodiments, a native oxide layer (the native oxide thickness is typically 1-3 nm) is already present on the surface of the substrate 102.

  The surface to be coated with the inorganic seed layer 140 can be cleaned by, for example, applying oxygen plasma before coating. In this process, an inductively coupled plasma (ICP) source is used to generate active oxygen radicals that etch organic materials to yield a clean oxide surface.

As shown in FIG. 3B, the inorganic seed layer 140 is deposited on the exposed surface of the fluid ejection device including the inner surface and the outer surface (eg, outside the nozzle layer 112 and the fluid flow path 104). The inorganic seed layer 140 of SiO ₂ is introduced into the nozzle layer 112 and the flow path module 104 by introducing SiCl ₄ and water vapor into a chemical vapor deposition (CVD) reactor containing the uncoated fluid discharge device 100. It can be formed on the exposed surface. After the pressure in the chamber is reduced, the valve between the CVD chamber and the vacuum pump is closed, and vapors of SiCl ₄ and H ₂ O are introduced into the chamber. The partial pressure of SiCl ₄ may be 0.05 to 40 Torr (eg 0.1 to 5 Torr), and the partial pressure of H ₂ O may be 0.05 to 20 Torr (eg 0.2 to 10 Torr). . The seed layer 140 may be deposited on a substrate that is heated to a temperature between about room temperature and about 100 degrees Celsius. For example, the substrate may not be heated, but the CVD chamber may be heated to 35 ° C.

In some embodiments of the CVD manufacturing process, the seed layer 140 is deposited in a two-step process with different ratios of H ₂ O partial pressure and SiCl ₄ partial pressure. Specifically, in the second step of disposing the outer portion 144 of the seed layer, the H ₂ O: SiCl ₄ partial pressure ratio is greater than the ratio in the first step of disposing the portion of the seed layer that is closer to the substrate 102. It can be large. The first step can be performed with a higher partial pressure of H ₂ O than the second step. In some embodiments, the H ₂ O: SiCl ₄ partial pressure ratio may be less than 2: 1 (eg, about 1: 1) in the first step and H ₂ O: SiCl _{4 in the second} step. The partial pressure ratio may be 2: 1 or more (for example, 2: 1 to 3: 1). For example, the partial pressure of SiCl ₄ may be about 2 Torr in both steps, and the partial pressure of H ₂ O may be about 2 Torr in the first step and about 4-6 Torr in the second step. . The second step may be performed for a sufficient duration so that the outer portion 144 has a thickness of about 50-500 angstroms.

Without being limited to any particular theory, a higher concentration of H ₂ O is trapped in the SiO ₂ matrix of the outer portion 144 by performing the second deposition step at a higher partial pressure ratio of H ₂ O: SiCl _4. Is done. As a result, a higher concentration of —OH groups can be present on the surface of the inorganic layer 140.

Instead of or in addition to performing the second deposition step at a higher partial pressure ratio of H ₂ O: SiCl ₄ , the second deposition step may be performed at a lower substrate temperature than the first step. For example, the first deposition step can be performed at about 50-60 ° C. for the substrate and the second deposition step at about 35 ° C., respectively. Without being limited to any particular theory, performing the second deposition step at a lower temperature also increases the concentration of —OH groups present on the surface of the inorganic layer 140.

In some embodiments of the manufacturing process, the entire seed layer 140 may be deposited in a single continuous process without changing the temperature or greater H ₂ O: SiCl ₄ partial pressure ratio. Again, without being limited to any particular theory, this can make the concentration of H ₂ O trapped in the SiO ₂ matrix more uniform across the seed layer 140.

  The total thickness of the inorganic seed layer 140 is about 5 nm to about 200 nm. For some fluids ejected, performance can be affected by the thickness of the inorganic layer. For some “difficult” fluids, a thick layer, eg, 30 nm or more (eg, 40 nm or more, or 50 nm or more) improves performance. Such “difficult” fluids include, for example, luminescent properties such as various conductive and luminescent polymers (eg, poly-3,4-ethylenedioxythiophene) (PEDOT) or Dow Chemical's DOW Green K2. Mention may be made of inks having a high chemical activity, such as inks containing polymers and also pigments and / or dispersants having a high chemical activity.

Next, the fluid ejection device can be subjected to an oxygen O ₂ plasma treatment process. Specifically, both the inner and outer surfaces of the inorganic seed layer 140 are exposed to O ₂ plasma. The oxygen plasma treatment can be performed, for example, in a Yield Engineering Systems anode-coupled plasma device with an O ₂ flow rate of 80 sccm, a pressure of 0.2 Torr, an RF power of 500 W, and a treatment time of 5 minutes.

As shown in FIG. 3C, the O ₂ plasma treatment can make the outer portion 142 of the silicon oxide seed layer 140 dense. For example, the outer portion 142 can have a density of 2.4 g / cm ³ or greater, and the lower portion of the seed layer 140 can have a density of about 2.0 g / cm ³ . Furthermore, the O ₂ plasma treatment was deposited with an outer portion (eg, outer portion 144) at a large H ₂ O: SiCl ₄ partial pressure ratio (eg, at a H ₂ O: SiCl ₄ pressure ratio greater than 2: 1). In some cases, it is more effective by densification. In such a case, the outer portion 142 can have a density of about 2.7 g / cm ³ . The outer portion 142 can have a thickness of about 40 angstroms.

  Next, as shown in FIG. 3D, a non-wetting coating 150 (eg, a layer of hydrophobic material) is deposited on the exposed surface of the fluid ejection device including both the outer and inner surfaces of the flow path 104. The non-wetting coating 150 is not brushed, rolled or spun but rather can be deposited using vapor deposition.

Non-wetting coating 150 can be deposited, for example, by introducing precursors and water vapor into a low pressure CVD reactor. The partial pressure of the precursor may be 0.05 to 1 Torr (eg 0.1 to 0.5 Torr), and the partial pressure of H ₂ O is 0.05 to 20 Torr (eg 0.1 to ₂ Torr) Also good. The deposition temperature may be from room temperature to about 100 ° C. For example, the coating process and the formation of the inorganic seed layer 140 may be performed by Applied MicroStructures, Inc. May be implemented using a Molecular Vapor Deposition (MVD) ™ device.

Suitable precursors for the non-wetting coating 150 include, by way of example, precursors that include molecules having non-wetting ends and ends that can be attached to the surface of the fluid ejection device. For example, one end may be used precursor molecule comprising a carbon chain second end is terminated with ₃ groups -SiCl with _a -CF ₃ group. Specific examples of suitable precursors for deposition on silicon surfaces include tridecafluoro-1,1,2,2-tetrahydrooctyltrichlorosilane (FOTS) and 1H, 1H, 2H, 2H-perfluorodecyl-tri Mention may be made of chlorosilane (FDTS). Other examples of non-wetting coatings include 3,3,3-trifluoropropyltrichlorosilane (CF ₃ (CH ₂ ) ₂ SiCl ₃ ) and 3,3,3,4,4,5,5,6, 6, - nonafluorohexyl trichlorosilane _{(CF 3 (CF 2) 3} (CH 2) 2 SiCl 3) and the like. Without being limited to any particular theory, when a precursor whose molecule has a -SiCl ₃ terminus (such as FOTS or FDTS) is introduced into the CVD reactor with water vapor, the precursor is then hydrolyzed and then -SiCl A film of molecules (single molecule) in which a siloxane bond is formed such that silicon atoms from _three groups are bonded to oxygen atoms from -OH groups on the inorganic layer 165 and the other (ie non-wetting) end is exposed. Layer, etc.).

  In some embodiments, the non-wetting coating 150 forms a self-assembled monolayer (ie, a single molecule layer). Such a non-wetting coating monolayer 150 can have a thickness of about 10-20 angstroms (eg, about 15 angstroms).

  In some embodiments, the non-wetting coating 150 forms a molecular assembly (eg, an assembly of fluorocarbon molecules). Such a non-wetting coating assembly 150 can have a thickness of about 50 to 1000 Angstroms. In order to form a non-wetting film assembly, the temperature of the substrate is set to a temperature lower than the temperature of the non-wetting film precursor. Without being limited to any particular theory, a low substrate temperature effectively causes aggregation of fluorocarbons on the seed layer 140. This can be accomplished by bringing the substrate support to a lower temperature than the gas manifold (eg, gas line or supply cylinder) used to deposit the non-wetting film. The temperature difference between the substrate support and the gas manifold (and possibly the substrate itself and the gas entering the chamber) may be about 70 ° C. For example, the substrate support may be cooled with liquid nitrogen, the substrate support may be about −194 ° C., and the gas manifold may be at room temperature (eg, about 33 ° C.). As another example, the substrate support may be cooled by a cooler to bring the substrate support to about −40 ° C. and the gas manifold to room temperature (eg, about 33 ° C.). As another example, the substrate support is maintained at about room temperature (eg, about 33 ° C.) and the gas manifold is heated to, eg, about 110 ° C.

  The molecular assembly is for example to form a monolayer of tridecafluoro-1,1,2,2-tetrahydrooctyltrichlorosilane (FOTS) or 1H, 1H, 2H, 2H-perfluorodecyltrichlorosilane (FDTS). It may be formed from precursors that may be used.

  As shown in FIG. 3E, a mask 160 is applied to the outer surface of the fluid ejection device (eg, at least a region surrounding the nozzle 128). The masking layer may be composed of various materials. For example, tape, wax, or photoresist can be used as a mask. Mask 160 protects the surface to which it is applied from removal or damage that occurs during the cleaning process (eg, from exposure to oxygen plasma) and / or from subsequent deposition (eg, from deposition of an overcoat layer). The mask 160 can have sufficiently low adhesion so that the underlying non-wetting coating 150 is removed without being removed, damaged, or substantially altered.

  As shown in FIG. 3F, the inner surface of the fluid path 104 of the fluid ejection device is subjected to a cleaning process (for example, a cleaning gas (for example, oxygen plasma) process) for removing a portion of the non-wetting film that is not covered by the mask 160. Is done. Oxygen plasma may be applied to the substrate in the chamber, or a source of oxygen plasma may be connected to the inlet of the fluid path. In the former case, the mask 160 prevents oxygen plasma outside the fluid ejection device in the chamber from removing the non-wetting film on the outer surface. In the latter case, the mask 160 prevents oxygen plasma from flowing through the orifice to remove the non-wetting coating on the outer surface (in this case, the mask need only cover the orifice itself).

  As shown in FIG. 3G, the mask 160 is removed after the cleaning step, thereby providing the fluid ejection device shown in FIGS. 1A and 1B. The final finished device is a fluid ejection device having an outer surface that is non-wetting and an inner surface that is more wettable than the non-wetting surface.

In an exemplary process, the silicon oxide seed layer is a two-step process (eg, H ₂ O in the second process) in which the second process is performed at a higher H ₂ O: SiCl ₄ partial pressure ratio than the first process. : SiCl ₄ partial pressure ratio is greater than 2: 1). The seed layer on both the inner and outer surfaces of the fluid ejection device is then oxygen plasma treated. A non-wetting coating is formed as a molecular assembly on both the inner and outer surfaces of the fluid ejection device, and the inner surface is further subjected to an oxygen plasma treatment to remove the non-wetting coating from the inner surface and on the outer surface. A molecular assembly remains.

In another exemplary process, the silicon oxide seed layer is deposited in a single step process of the second step with a “medium” H ₂ O: SiCl ₄ partial pressure ratio (eg, equal to about 2: 1). The The seed layer on both the inner and outer surfaces of the fluid ejection device is then oxygen plasma treated. A non-wetting coating is formed as a monolayer (ie, a layer of a single molecule) on both the inner and outer surfaces of the fluid ejection device, and the inner surface is further oxygenated to remove the non-wetting coating from the inner surface. A plasma treatment is applied, leaving a non-wetting monolayer on the outer surface.

  In another embodiment, as shown in FIG. 4, the fluid ejection device 110 does not have a deposited seed layer 140 and the non-wetting coating 150 is placed directly on the natural surface of the fluid ejection device (which may include native oxide). Molecular assembly.

  As shown in FIG. 5A, an overcoat layer 170 is deposited on the inner surface (eg, on the surface of the seed layer 140) of the fluid ejection device, except on the outer surface of the non-wetting coating 150, forming the fluid pathway. be able to.

  First, the cleaning process may not be completely effective to remove the non-wetting coating from the inner surface (particularly the nozzle area). However, the cleaning process is sufficiently effective for the subsequently deposited overcoat layer to adhere and cover the non-wetting properties that remain on the inner surface of the fluid ejection device. Without being limited to any particular theory, it may be left on the inner surface with areas or regions of non-wetting coating and other areas or regions of the exposed seed layer that are large enough to allow adhesion of the overcoat layer. Alternatively, non-wetting on the inner surface may be compromised to allow adhesion of the overcoat layer.

  Second, even though the cleaning process was effective enough to completely remove the non-wetting coating 150 from the inner surface, when the outer portion of the seed layer 140 is deposited at a high water vapor partial pressure, the inorganic layer 140 The surface of the outer part of can have a higher concentration of -OH groups, which can make the inorganic layer more vulnerable to chemical erosion by some liquids.

  Fabrication of the fluid ejection device can proceed as described above with respect to FIGS. 3A-3F, as shown in FIG. 5A. However, as shown in FIG. 5B, before the mask 160 is removed, the overcoat layer 170 is deposited on the exposed (eg, unmasked) inner surface of the fluid ejection device. After the overcoat layer 170 is deposited, the mask 160 can be removed. However, in some embodiments, the material of the non-wetting coating may be such that the overcoat layer does not adhere to the non-wetting coating 150 during deposition (and thus prior to deposition of the overcoat layer). The overcoat layer does not adhere to and does not form on the non-wetting coating 150).

The overcoat layer 170 provides an exposed surface that is more wettable than the non-wetting coating 150, for example, within the finished device. In some embodiments, the overcoat layer 170 is composed of an inorganic oxide. For example, the inorganic oxide can include silicon, for example, the inorganic oxide can be SiO ₂ . Overcoat layer 170 may be deposited by conventional techniques such as CVD as described above. As described above, a cleaning step (eg, oxygen plasma) can be used to remove the non-wetting film from the inner surface of the fluid ejection device so that the overcoat layer adheres to the inner surface. Furthermore, the same apparatus can be used to clean the surface to be deposited and to deposit the overcoat layer.

  In some embodiments, the overcoat layer 170 is deposited under the same conditions as the seed layer 140 and has essentially the same material properties (eg, the same wettability). The overcoat layer 170 may be thinner than the seed layer 140.

  In some embodiments, the overcoat layer 170 is deposited under different conditions than the seed layer 140 and has different material properties. Specifically, the overcoat layer 170 may be deposited at a higher temperature than the seed layer 140 or at a lower water vapor pressure. Accordingly, the surface of the overcoat layer 170 can have a lower —OH concentration than the surface of the seed layer 140. Therefore, the overcoat layer is less susceptible to chemical erosion by the discharged liquid.

In some embodiments, overcoat layer 170 can also cover exposed surfaces (eg, exposed inner and outer surfaces) of mask 160. For example, the masked fluid ejection device 100 may be placed in a CVD reactor into which precursors of the overcoat layer 170 (eg, SiCl ₄ and water vapor) are introduced. In such an embodiment, an overcoat layer is formed on the outer surface of the mask and on the portion of the inner surface that covers the nozzle. Then, when the mask is removed from the non-wetting coating 150, the overcoat layer on the mask is removed.

In another embodiment, the overcoat layer 170 does not cover the exposed outer surface of the mask 160. This is due to either the overcoat layer 170 being deposited only on the inner surface (eg, the portion of the inner surface over the opening) or because the overcoat layer does not physically adhere to the mask. In the former case, for example, the precursor (for example, SiCl ₄ and water vapor) of the overcoat layer 170 is only on the inner exposed surface of the fluid ejection device (that is, the surface that comes into contact with the fluid ejected from the fluid ejection device). As introduced, it can be realized by providing the fluid ejection device 100 with an appropriate attachment. In these embodiments, the mask 160 can be applied to a sufficiently localized area surrounding the nozzle 128 to prevent the overcoat layer from reaching the outer surface area.

Optionally, after deposition of overcoat layer 170, overcoat layer 140 may be subjected to an oxygen O ₂ plasma treatment step. Specifically, the overcoat layer 170 on the inner surface is exposed to O ₂ plasma. Without being limited to any particular theory, the O ₂ plasma treatment can make the outer portion of the overcoat layer 170 dense. The oxygen plasma can be applied to the substrate in a chamber different from that used to deposit the SiO ₂ layer (eg, by anodic coupled plasma).

In an exemplary process, the seed layer 140 is deposited with a H ₂ O: SiCl ₄ partial pressure ratio (eg, at a higher H ₂ O partial pressure) that is greater than the overcoat layer 170, but the seed layer 140 and over Both coat layers 170 are O ₂ plasma treated.

  In summary, in the final product, the surface surrounding the nozzle 128 (eg, the outer surface) is non-wetting, and the surface that is in contact with the fluid being discharged (eg, the inner surface) is more wettable than the surface coated with the non-wetting coating. Have

  A number of embodiments have been described. For example, the nozzle layer may be made of a material different from that of the flow path body, and similarly, the film layer may be made of a material different from that of the flow path body. The inorganic seed layer may be formed by sputtering instead of being deposited by CVD. It will be understood that various other modifications can be made without departing from the spirit and scope of the invention.

Claims (10)

A substrate having an outer surface and an inner surface defining a fluid flow path to an orifice in the outer surface;
A seed layer covering at least a portion of the outer surface of the substrate and having a composition different from that of the substrate, the seed layer having an inner portion having a first density and an outer portion farther from the substrate than the inner portion A seed layer, wherein the outer portion has a second density higher than the first density;
A non-wetting coating on the seed layer, which covers at least a portion of the outer surface and is substantially absent in the flow path;
Only including,
The first density is about 2.0 g / cm ³ ;
Fluid ejection device. A substrate having an outer surface and an inner surface defining a fluid flow path to an orifice in the outer surface;
A seed layer covering at least a portion of the outer surface of the substrate and having a composition different from that of the substrate, the seed layer having an inner portion having a first density and an outer portion farther from the substrate than the inner portion A seed layer, wherein the outer portion has a second density higher than the first density;
A non-wetting coating on the seed layer, which covers at least a portion of the outer surface and is substantially absent in the flow path;
Only including,
The second density is at least 2.4 g / cm ³ ;
Fluid ejection device. The fluid ejection device of claim 2 , wherein the second density is about 2.7 g / cm ³ . A substrate having an outer surface and an inner surface defining a fluid flow path to an orifice in the outer surface;
A seed layer covering at least a portion of the outer surface of the substrate and having a composition different from that of the substrate, the seed layer having an inner portion having a first density and an outer portion farther from the substrate than the inner portion A seed layer, wherein the outer portion has a second density higher than the first density;
A non-wetting coating on the seed layer, which covers at least a portion of the outer surface and is substantially absent in the flow path;
Only including,
The second density is at least about 0.3 g / cm ³ higher than the first density ;
Fluid ejection device. A substrate having an outer surface and an inner surface defining a fluid flow path to an orifice in the outer surface;
A seed layer covering at least a portion of the outer surface of the substrate and having a composition different from that of the substrate, the seed layer having an inner portion having a first density and an outer portion farther from the substrate than the inner portion A seed layer, wherein the outer portion has a second density higher than the first density;
A non-wetting coating on the seed layer, which covers at least a portion of the outer surface and is substantially absent in the flow path;
Only including,
The outer portion has a thickness of about 40 Å;
Fluid ejection device. The non-wetting coating is composed of a molecular assembly, a fluid ejection device according to any one of claims 1 to 5. The seed layer comprises silicon dioxide, the fluid ejecting apparatus according to any one of claims 1 to 6. The fluid ejection device according to claim 7 , wherein the substrate is single crystal silicon. The fluid ejection device according to claim 7 or 8 , wherein the non-wetting coating comprises siloxane chemically bonded to the seed layer. The non-wetting coating is at least one precursor of the group consisting of tridecafluoro 1,1,2,2 tetrahydrooctyltrichlorosilane (FOTS) and 1H, 1H, 2H, 2H perfluorodecyl-trichlorosilane (FDTS). The fluid ejection device according to claim 9 , comprising molecules to be configured.

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